An Air Turbine Starter (ATS) system is commonly utilized to initialize Main Engine Start (MES) of an air-started gas turbine engine. A typical ATS system contains an ATS and a Starter Air Valve (SAV), which are fluidly coupled and removably installed on the Accessory Gearbox (AGB) of an engine. The ATS itself may include a housing, an air turbine rotatably mounted in the housing, and an ATS output shaft coupled to the air turbine and projecting from the housing. A gear train and a clutch may also be disposed in the housing between the air turbine and the ATS output shaft to provide a desired gear reduction and to prevent back-driving of the air turbine. When the ATS is installed on an AGB, the gearing of the AGB mechanically links the ATS output shaft to a spool of the engine. During MES, the SAV is opened to allow pressurized air to flow into the ATS driving rotation of the air turbine and the ATS output shaft. Rotation of the ATS output shaft, in turn, drives rotation of the engine spool or spools through the AGB. After MES has been achieved, the SAV is closed and pressurized airflow to the ATS ceases. The ATS system may thus remain inactive until MES is again required. However, even when the ATS is inactive, the ATS output shaft and portions of the ATS clutch may continue to rotate rapidly as the output shaft is driven through the AGB by rotation of the engine spool(s).
In addition to the above-mentioned components, an ATS is also commonly equipped with a shaft-driven oil pump, which draws oil from a sump and injects the oil directly into the clutch or onto a nearby rotating body such that oil is thrown into the clutch via centrifugal forces during ATS operation. After flowing through the clutch, the oil returns to the sump by gravity flow to form a relatively simple, self-contained lubrication system. While providing certain advantages in view of its simplicity, such an ATS lubrication system is limited in several respects. For example, the ATS lubrication system typically lacks means for filtering, pressurizing, cooling, or otherwise conditioning the oil. As a result, the oil contained within the ATS may be prone to gradual fouling due to, for example, heat exposure and contamination resulting from seal degradation. Additionally, the ATS typically contains a relatively small volume of oil, which may further diminish due to leakage and decay occurring over the service life of the ATS. Issues relating to oil quality and quantity can thus increase maintenance requirements and impose undesirable limitations on the overall operational lifespan of an ATS.
It is thus desirable to provide an ATS having enhanced lubrication properties, which could favorably reduce maintenance requirements and prolong the operational lifespan of the ATS. More generally, it would be desirable to provide an ATS system including such an ATS and also having a reduced weight, complexity, envelope, and part count as compared to conventional ATS systems. It would also be desirable if, in at least some embodiments, the ATS system could be designed to provide high levels of modularity to facilitate in-line repair and replacement of components included within the ATS system. Other desirable features and characteristics of the present invention will become apparent from the subsequent Detailed Description and the appended Claims, taken in conjunction with the accompanying Drawings and the foregoing Background.